Electrostatic periodically focused backward-wave oscillator

A low voltage electrostatic periodically focused BWO has been developed which operates over most of X-band and delivers a maximum output power of 20 m.w. This device employs a hollow beam and a bifilar helix circuit. This is a remarkable result as the performance of such a tube is known to be extremely critical to the quality of the focusing. It experimentally demonstrates the rigid focusing predicted theoretically for the bifilar arrangement. Theoretical and experimental investigations have been conducted to determine the feasibility of using a modified focusing scheme which employs a uniform radial electric field in addition to the periodic fields of the bifilar helix. An improved S-band model under construction is expected to give about 50 m.w. output over a 2 to 1 bandwidth with maximum beam voltage less than 1 KV. The test results from this tube will be presented.